The present invention relates generally to control systems for movable apparatus, and particularly to electronic controllers for automotive power seat systems.
Automotive seats are frequently equipped with power systems for selectively adjusting the position of the seats in several directions. One such system provides for three manually actuable switches which allow seat adjustments in six different directions. The first switch is a 4-way "joy-stick" type switch for controlling the movement in the forward or reverse directions and the upward or downward directions. The remaining two switches are each 2-way momentary toggle switches, one of which allows for front up or down movement and the other allows rear up or down movement.
Typically, two types of motive power systems have been employed for adjusting the direction of power seats in automobiles. One such motive power system comprises three separate d.c. motors which are each coupled to a rack mechanism for providing the appropriate number of position adjustments. A second type of motive power system employs a single motor coupled to three separate clutch mechanisms for selectively actuating three different rack assemblies. Both systems generally provide a control circuit which includes one or more "joy-stick" and/or toggle switches, and particular adjustments are made by actuating the appropriate switch and holding the switch in its actuated state until the desired seat position in the direction chosen is reached.
Because most automobiles are frequently driven by at least two people of different stature, such as a husband and wife, various control systems have recently been developed which provide means for storing different desired seat positions in a memory device for subsequent selective retrieval. In such systems, once a desired seating position has been established and stored in the memory device provided, the controller will automatically return the seat to the desired position upon the actuation of a separate "recall" switch. Typically, such control systems include two recall switches for selectively recalling either of two previously stored seating positions.
Accordingly, it is a principle object of the present invention to provide an improved electronic controller for adjusting the position of a movable apparatus, which features memory means for storing a plurality of desired positions for the movable apparatus.
It is a more specific object of the present invention to provide an improved electronic controller in an automotive power seat system having motive power means adapted to adjust the position of a seat and a first operator actuable switch group for generating command signals for manually adjusting the position of the seat.
It is another object of the present invention to provide an improved electronic controller which tracks the position of the automobile seat by detecting predetermined fluctuations in the current signal from a d.c. power source supplying electrical power to the motive power means for the power seat system.
It is an additional object of the present invention to provide an improved electronic controller which quickly detects a "stall" condition when the rack mechanism encounters a mechanical stop by monitoring the time between the predetermined current fluctuations.
It is also an object of the present invention to provide an improved electronic controller which features a "retract" mode which will cause the seat to assume its fully retracted and down reference position when both of the recall switches in a second operator actuable switch group are simultaneously actuated for permitting easy ingress egress from the automobile.
It is a further object of the present invention to provide an improved electronic controller which features an "abort" function, whereby actuation of any operator actuable switch in the first switch group will halt the execution of a previous "recall" or "retract" command currently in process.
It is a further object of the present invention to provide an improved electronic controller which includes a provision for maintaining standby power to the memory means for a predetermined time after the battery has been removed from the automobile or otherwise disconnected.
It is yet another object of the present invention to provide an electronic controller which includes a "reverse" function, whereby the motor of the motive power means is operated in the reverse direction momentarily when the motor is to be deactivated to ensure proper disengagement of a clutch mechanism.
To achieve the foregoing objects, the novel electronic controller according to the present invention features a microcomputer which receives command signals from a first and second group of operator actuable switches, present position signals from a monitoring circuit, and stored position signals from a memory circuit, for generating control signals for directing a motive power means to adjust the position of an automobile seat. In a standby mode, only the memory circuit is supplied with electrical power in order to minimize the power drain on the d.c. power source for the motive power means, i.e. typically an automobile battery. However, whenever any of the operator actuable switches are actuated to modify the position of the seat, a run mode is assumed and power is supplied to the microcomputer. An initialization sequence is commenced which includes down loading the stored position data from the memory circuit into the internal RAM memory circuit of the microcomputer.
The monitoring circuit includes transducer means for sensing the current draw from the d.c. power source, and differentiating means connected to the transducer means for generating a pulse concomitantly with each commutation of the motor from the motive power means. These pulse position signals are sent to the interrupt port of the microcomputer and then counted by an internal timer for determining the present position of the automotive seat. An important feature of the present invention is the use of these pulse position signals to determine a "stall" condition which occurs when the rack mechanism has encountered a mechanical stop, such as when the seat reaches its full forward position. The time between these pulses is monitored and a stall condition is determined when the time betwen these pulses exceeds a predetermined period (approximately 6 milliseconds). One advantage of this detection technique is that a stall condition may be detected relatively rapidly in comparision with prior detection techniques, such as monitoring the rate at which the current draw for the motor increases with respect to time.